Doping apparatus, doping method, and method for fabricating thin film transistor

ABSTRACT

It is an object of the present invention to provide a doping apparatus, a doping method, and a method for fabricating a thin film transistor that can carry out doping to the carrier concentration which is optimum for obtaining the desired electric characteristic non-destructively and in an easy manner. In accordance with the present invention, an electric characteristic of a semiconductor element (threshold voltage in a transistor and the like) is correctly and precisely monitored by using a contact angle, and is controlled by controlling a doping method. In addition, the present invention can be momentarily acquired information by in-situ monitoring the characteristic and can be fed back without a time lag.

This application is a Divisional of application Ser. No. 10/910,623filed Aug. 4, 2004 now U.S. Pat. No. 7,250,312, now Allowed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a doping apparatus and a doping method,more specifically to doping technology used for forming a dopant regionsuch as source and drain regions in a field-effect transistor (FET).

2. Description of the Related Art

In semiconductor elements (devices) such as a field-effect transistorand a thin-film transistor, doping is carried out to control theirelectric characteristics. The doping is a method for introducing adopant such as arsenic (As), boron (B), and phosphorus (P) into asemiconductor film. Depending on the type of the dopant introduced intothe semiconductor element, the semiconductor elements can be obtained ptype in which holes are the majority carrier and n type in whichelectrons are the majority carrier. Therefore, electric characteristicsof semiconductor elements (for example, a threshold voltage in thin-filmtransistors) have been controlled by the amount of dopant (dosage) whichis doped, activation ratio of the dopant, and carrier concentration.

The activation ratio of a dopant is represented by the ratio of theamount of a dopant introduced in a semiconductor film and the amount ofactually activated dopant. The activated dopant generates carriers. Whenthe activation ratio of a dopant is 100%, the concentration of a dopantbecomes equal to the concentration of carriers.

Characteristics of the elements have been conventionally inspected uponcompletion of semiconductor element fabrication. This information is fedback to a fabrication process and the doping method such as the amountof a dopant and doping rate is adjusted.

On the other hand, secondary ion mass spectroscopy (SIMS), spreadresistance method (SR), and the like are used as methods for measuringthe aforementioned dopant concentration (for example, see PatentDocument 1).

[Patent Document 1]

Japanese Patent Laid-Open No. H11-23498

SUMMARY OF THE INVENTION

However, secondary ion mass spectroscopy (SIMS) and spread resistancemethod (SR) are destructive inspections and are not suitable forconducting measurements on the substrates in a real production line.Furthermore, the concentration that can be measured with secondary ionmass spectroscopy (SIMS) is the concentration of the introduced dopantand this method cannot measure the accurate concentration of carriers.Further, the spread resistance method (SR) cannot clarify theconductivity type of the carriers.

Further, if those methods are used for measuring the electriccharacteristics of a FET, conducting the feedback upon completion of theentire process causes poor efficiency and a time delay (time lag), whichresults in inaccurate information.

It is an object of the present invention to provide a doping apparatusand a doping method that can carry out doping to the carrierconcentration which is optimum for obtaining the desired electriccharacteristics non-destructively and in an easy manner. In addition, itis another object of the present invention is to momentarily acquireinformation by in-situ monitoring the characteristics and to enable thedoping without a time lag.

In accordance with the present invention, characteristics of asemiconductor element (threshold voltage in a transistor and the like)are correctly and precisely monitored by using a contact angle. Acontact angle also corresponds to slight changes in the electriccharacteristics of a semiconductor.

A contact angle, as represented by Formula 1, depends on the surfacetension (surface free energy) of a substance.γ_(S)=γ_(L) cos θ+γ_(SL)  [Formula 1]In Formula 1, γ_(S) is the surface tension of a solid, γ_(L) is thesurface tension of a liquid, θ is a contact angle (liquid wettingangle), γ_(SL) is the interface tension between the solid and theliquid. The smaller is the contact angle, the better is wetting with theliquid. For example, if the liquid is water, the smaller is the contactangle of water, the more hydrophilic is the solid surface and theincrease in the contact angle is considered as hydrophobicity. Formula 1demonstrates that for the same liquid, the contact angle is increasedand the surface is less wetted, and the so-called wettability isdegraded as the surface tension of the solid decreases.

In accordance with the present invention, the electric characteristicsof a semiconductor element (threshold voltage in a transistor and thelike) are correctly and precisely monitored by using a contact angle,and the characteristics are controlled by controlling the doping method.

One of the doping apparatuses in accordance with the present inventioncomprises means for doping a dopant element providing one conductivitytype into a semiconductor layer, means for measuring a contact angle ofthe surface of the semiconductor layer, means for judging theconductivity type and carrier concentration of the semiconductor layerfrom the measured contact angle, and means for feeding back the amountof the dopant element providing one conductivity type that should bedoped into the semiconductor layer to the means for doping based on thejudgment results.

One of the doping apparatuses in accordance with the present inventioncomprises means for doping a dopant element providing one conductivitytype into a semiconductor layer, means for cleaning the surface of thesemiconductor layer, means for measuring a contact angle of the surfaceof the semiconductor layer, means for judging the conductivity type andcarrier concentration of the semiconductor layer by the measured contactangle, and means for feeding back the amount of the dopant elementproviding one conductivity type that should be doped into thesemiconductor layer to the means for doping based on the judgmentresults.

In the above-described structure, means for cleaning the surface of thesemiconductor layer is means for chemically removing an oxide film andthe like which is formed in the course of time on the surface of thesemiconductor layer in order to measure the correct contact angle of thesemiconductor surface. The oxide film may be removed by spin applying anaqueous solution containing hydrofluoric acid and etching.

The contact angle may be measured with a liquid allowing for precisemeasurements on the semiconductor film. For example, the carrierconcentration and conductivity type of the semiconductor layer can beestimated by using water and measuring the contact angle of water on thesemiconductor film surface. A Dopant such as arsenic (As), boron (B), orphosphorus is activated and becomes a carrier. The carrier concentrationin the semiconductor layer and the conductivity type thereof areanalyzed and judged by using a contact angle as a sensor, and thecharacteristics of the semiconductor (threshold voltage of a transistorand the like) using this semiconductor layer are analyzed. Theinformation obtained is fed back to the means for doping the dopantelement providing one conductivity type and doping of the dopant elementproviding one conductivity type is carried out so that the electriccharacteristics of the semiconductor element which are assessed by acontact angle assume the appropriate values.

One doping method in accordance with the present invention comprises thesteps of judging the conductivity type and carrier concentration of asemiconductor layer and determining the amount of a dopant of oneconductivity type that should be doped into the semiconductor layer bymeasuring a contact angle of the surface of the semiconductor layer.

One doping method in accordance with the present invention comprises thesteps of exposing the surface of a semiconductor layer, and judging theconductivity type and carrier concentration of the semiconductor layerand determining the amount of a dopant of one conductivity type thatshould be doped into the semiconductor layer by measuring a contactangle of the surface of the semiconductor layer.

One doping method in accordance with the present invention comprises thesteps of exposing the surface of a semiconductor layer, judging theconductivity type and carrier concentration of the semiconductor layer,determining the amount of a dopant of one conductivity type that shouldbe doped into the semiconductor layer by measuring a contact angle ofthe surface of the semiconductor layer, and controlling the thresholdvoltage of a transistor.

In the above-described configuration, a contact angle of the surface ofthe semiconductor layer may be measured after chemically removing anoxide film and the like formed in the course of time on the surface ofthe semiconductor layer in order to measure the correct contact angle ofthe semiconductor surface. The oxide film may be removed by spinapplying an aqueous solution containing hydrofluoric acid and etching.

A contact angle may be measured with a liquid allowing for precisemeasurements on the semiconductor film. For example, at least one of thecarrier concentration and the conductivity type of the semiconductorlayer can be estimated by using water and measuring a contact angle ofwater on the semiconductor film surface. A dopant such as arsenic (As),boron (B), or phosphorus (P) is activated and becomes a carrier. Thecarrier concentration in the semiconductor layer and the conductivitytype thereof are judged by using a contact angle as a sensor, and theelectric characteristics of the semiconductor (threshold voltage of athin film transistor) using this semiconductor layer are analyzed. Thedoping conditions are determined and fed back to the doping process sothat the electric characteristics of the semiconductor (thresholdvoltage of a thin film transistor) which are assessed by a contact angleassume the appropriate values. If necessary, the doping conditions arecontrolled and doping into the semiconductor layer is conducted. Thedoping process is carried out, while the information is fed back, tillthe carrier concentration and conductivity type thereof are optimized.The semiconductor layer in which the optimum carrier concentration andconductivity type have been attained is advanced to subsequentprocessing.

One method for fabricating a thin film transistor in accordance with thepresent invention comprises the steps of exposing the surface of asemiconductor layer, measuring a contact angle at the surface of thesemiconductor layer, judging the conductivity type and carrierconcentration of the semiconductor layer from the measured contactangle, determining the amount of a dopant element providing oneconductivity type that should be doped into the semiconductor layerbased on the judgment results, and then doping the dopant elementproviding one conductivity type into the semiconductor layer.

One method for fabricating a thin film transistor in accordance with thepresent invention comprises the steps of exposing the surface of asemiconductor layer, measuring a contact angle at the surface of thesemiconductor layer, judging the conductivity type and carrierconcentration of the semiconductor layer from the measured contactangle, determining the dose quantity of a dopant element providing oneconductivity type aimed at controlling the threshold voltage of atransistor in the semiconductor layer based on the judgment results, andthen doping the dopant element providing one conductivity type into thesemiconductor layer.

In the above-described configuration, a contact angle of the surface ofthe semiconductor layer may be measured after chemically removing anoxide film and the like formed in the course of time on the surface ofthe semiconductor layer in order to measure the correct contact angle ofthe semiconductor surface. The oxide film may be removed by spinapplying an aqueous solution containing hydrofluoric acid and etching.

A contact angle may be measured with a liquid allowing for precisemeasurements on the semiconductor film. For example, the carrierconcentration and conductivity type of the semiconductor layer can beestimated by using water and measuring a contact angle of water on thesemiconductor film surface. A dopant such as arsenic (As), boron (B), orphosphorus (P) is activated and becomes a carrier. The carrierconcentration in the semiconductor layer and the conductivity typethereof are judged by using a contact angle as a sensor, and theelectric characteristics of the semiconductor (threshold voltage of athin film transistor) using this semiconductor layer are analyzed. Thedoping conditions are determined and fed back to the doping process sothat the electric characteristics of the semiconductor (thresholdvoltage of a thin film transistor) which are assessed by a contact angleassume the appropriate values. If necessary, the doping conditions arecontrolled and doping into the semiconductor layer is conducted. Thedoping process is carried out, while the information is fed back, tillthe carrier concentration and conductivity type thereof are optimized.The semiconductor layer in which the optimum carrier concentration andconductivity type have been attained is advanced to subsequentprocessing.

In accordance with the present invention, the characteristics of asemiconductor can be measured non-destructively and in an easy manner,and the optimum carrier concentration and conductivity type thereof canbe obtained by feeding back the information. Because of thenon-destructive inspection and simple manner, in-situ measurements ofactual substrates are possible. Because monitoring can be conducted onactual substrates, inaccuracy of measurements is extremely small.

Further, the characteristics of the semiconductor can be momentarily andaccurately comprehended non-destructively and in an easy manner byin-situ monitoring the characteristics, and doping can be conductedunder optimum conditions allowing the desired characteristics to beobtained by feeding back this information to the process. Therefore,there is no time lag in the feedback and the yield is increased.

In accordance with the present invention, the characteristics of asemiconductor can be measured non-destructively and in an easy manner,and the optimum doping conditions can be determined by feeding back theinformation. Because of the non-destructive inspection and simplemanner, in-situ measurements of substrates in an actual production lineare possible. Because monitoring can be conducted on the substrates,inaccuracy of measurements is extremely small. Furthermore, theactivation ratio of a dopant in the semiconductor, which is a factorrelating to actual electric characteristics, can be accurately measuredand the conductivity type of a dopant can be distinguished.

The present invention can provide a doping apparatus and a doping methodwith which the characteristics of a semiconductor can be momentarily andaccurately comprehended non-destructively and in an easy manner byin-situ monitoring the characteristics, and doping can be conductedunder optimum conditions allowing the desired characteristics to beobtained by feeding back this information to the process. The presentinvention can also provide a method for the fabrication of a thin filmtransistor using the doping apparatus and the doping method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a configuration of the present invention.

FIG. 2 is a diagram showing a configuration of the present invention.

FIG. 3 is a diagram showing a configuration of the present invention.

FIGS. 4A to 4C are cross-sectional views showing a fabricating processof an active matrix substrate.

FIGS. 5A to 5C are cross-sectional views showing a fabricating processof an active matrix substrate.

FIG. 6 is a cross-sectional view of a light-emitting display device ofthe present invention.

FIGS. 7A to 7F are views showing an example of display device of thepresent invention.

FIGS. 8A to 8C are views showing an example of display device of thepresent invention.

FIGS. 9A to 9C are cross-sectional views showing a fabricating processof an active matrix substrate.

DETAILED DESCRIPTION OF THE INVENTION Embodiment Mode

Embodiment modes of the present invention will be described withreference to the accompanying drawings. Note that the present inventioncan be implemented in various modes, and it is understood easily bythose skilled in the art that embodiment modes and details of theinvention can be variously changed without departing from the spirit andscope of the invention. Therefore, the present invention is notconstrued with a limitation on the contents of the embodiment modes.

FIG. 1 is a flow chart illustrating the present invention. First, acontact angle at the surface of a semiconductor layer is measuredthrough the preprocessing and up to a doping process and thecharacteristics of the semiconductor layer are studied. The carrierconcentration and conductivity type are judged by the measuredinformation.

The measured information is checked up with the conditions which areoptimum for obtaining the desired characteristics and the carrierconcentration and conductivity type thereof are verified. Based on theverification results, the additional doping is carried out, ifnecessary, and the semiconductor film with the optimized carrierconcentration and conductivity type thereof is advanced to subsequentprocessing.

A doping apparatus in accordance with the present invention is shown inFIG. 2. The reference numeral 100 stands for a doping chamber, 101—asemiconductor film, 102—an ion source, 103—a delivery chamber, 104—atransportation chamber, 105—a contact angle measurement chamber, 106—aprocessing chamber, 107—a load/unload chamber, 108—a transportationunit, 109—a contact angle measurement device, 110—a medium for loadingthe measurement information, 111—an analytical unit, 112—a control unit,and 113—a control unit of a doping apparatus.

The semiconductor film 101 that was introduced into the transportationchamber 104 from the load/unload chamber 107 is again transported to thepreprocessing chamber 106 via the delivery chamber 103 and thetransportation chamber 104. In the preprocessing chamber 106, thesurface of the semiconductor layer is preprocessed for contact anglemeasurements. In the present embodiment, it order to conduct accuratemeasurements on the surface of the semiconductor layer, an oxide filmthat was formed on the surface of the semiconductor layer is removedwith hydrofluoric acid (HF) as the preprocessing. The preprocessedsemiconductor film 101 is introduced into the contact angle measurementchamber 105 via the transportation chamber 104.

In the contact angle measurement chamber 105 provided with means formeasuring a contact angle, there are provided the contact anglemeasurement device 109 and medium 110 for storing and transmitting themeasurement information. The medium 110 for storing and transmitting themeasurement information comprises means for loading images, a computerunit for conducting image processing, and an output unit for outputtingthe values of contact angle. For example, a charge coupled element (CCD)camera 133 is used as the means for loading images, the images areloaded, and the information is transmitted to the analytical unit 111with the output unit. Instead of the CCD camera, an image sensor using acomplimentary metal oxide semiconductor (CMOS) can be also used as themeans for loading the images. The details are shown in FIG. 3. In thepresent embodiment, the analysis is conducted, for example, by a tangentline method by using a liquid drop method, but such as a gradientmethod, a perpendicular plate immersion method, and a downfall methodmay be also used. The analysis may also use a θ/2 method or athree-point click method. With the θ/2 method, a drop is assumed as partof a circle and the result is derived from a geometric theorem. With thethree-point click method, a contact angle is measured by clicking onepoint on the circumference of a circle and a solid-liquid contact pointof the loaded drop image on a monitor screen and conducting processingwith a computer. The three-point click method essentially involvesclicking on three points, but with huge liquids such that cannot beassumed to have a perfect round shape, more accurate measurements ofcontact angle can be conducted by clicking on four or more points.

The contact angle measurement chamber 105 equipped with the means formeasuring a contact angle, as shown in FIG. 3, is provided with thecontact angle measurement device 109 having a liquid dropping nozzle130. Furthermore, there is also provided the medium 110 for storing andtransferring the measured information, this medium comprising a camera133 which is means for loading the images, a computer unit forconducting image processing, and an output unit for outputting thevalues of a contact angle. The liquid 131 that was dropped from theliquid dropping nozzle 130 onto a semiconductor film 132 assumes a dropshape shown in FIG. 3. The relationship between the surface tensionγ_(S) of a solid, the surface tension γ_(L) of a liquid, the contactangle (liquid wetting angle) θ, and the interface tension γ_(SL) betweenthe solid and the liquid is represented by the above-describedFormula 1. The images loaded by the camera 133 are analyzed by imageprocessing and the values of contact angle are outputted. In the presentembodiment, the drop image is loaded via the camera 133 by using atangent line method and image processing, analysis, and output areconducted with a computer. However, the present embodiment is notlimited, provided that the contact angle can be measured.

Characteristics of the semiconductor film are judged by the informationon the carrier concentration and conductivity type that are made clearby the measured values of contact angle. In the analytic device 111which is means for judging the conductivity type and carrierconcentration of the semiconductor layer by the contact angle measured,a contact angle is measured by above-described contact angle measurementmethod, and the carrier concentration and conductivity type thereof areanalyzed and judged. The analyzed information is transmitted to thecontrol unit 112. A contact angle changes following changes in thecarrier concentration, and the value thereof and the mode of changingalso differ depending on the dopant element creating the carriers.Therefore, the measured value of the contact angle is compared with thevalue of contact angle at an optimum concentration of carriers createdby the dopant that was doped, and if the concentration is small, dopingmay be conducted. In other words, the amount (dose) of the dopantelement that should be doped into the semiconductor layer is determined.

The control unit 112 functions as means for feeding back the amount ofthe dopant element providing one conductivity type that should be dopedinto the semiconductor layer to the doping means based on the judgmentresults. If doping is necessary based on this information, the controlunit 112 indicates doping to the control unit 113 of the doping unit.The control unit of the doping unit that received the indicationconducts doping of a dopant into the semiconductor film 101 in thedoping chamber 100 via the reception chamber 103. Then, a contact angleof the semiconductor layer surface is measured again and doping into thesemiconductor layer is conducted till the carrier concentration optimumfor obtaining the desired characteristics is obtained. If the surface ofthe semiconductor layer has not been exposed, then the preprocessing iscarried out in the above-described manner prior to the contact anglemeasurement.

In accordance with the present invention, the characteristics of asemiconductor can be measured non-destructively and in an easy manner,and optimum doping conditions can be determined by feeding back theinformation. Because of the non-destructive inspection and simplemanner, in-situ measurements of substrates in actual production line arepossible. Because monitoring can be conducted on actual substrates,inaccuracy of measurements is extremely small. Further, the activationratio of the dopant in the semiconductor, which is a factor relating toactual electric characteristics, can be accurately measured and theconductivity type of the semiconductor can be also distinguished.

The present invention can provide a doping apparatus and a doping methodby which the characteristics of a semiconductor can be momentarily andaccurately comprehended non-destructively and in an easy manner byin-situ monitoring the characteristics, and doping can be conductedunder optimum conditions allowing the desired characteristics to beobtained by feeding back this information to the process. The presentinvention can also provide a method for the fabrication of a thin filmtransistor using the doping apparatus and the doping method.

Embodiment 1

In the present embodiment, a method for fabricating an active matrixsubstrate by using the present invention will be explained withreference to FIG. 4, FIG. 5, and FIG. 9. An active matrix substrate hasa plurality of TFT, but the explanation relates to a case where thesubstrate has a drive circuit portion having an n-channel TFT and ap-channel TFT and a pixel portion having an n-channel TFT and ap-channel TFT.

A silicon nitride oxide film with a thickness of 10-200 nm (preferably,50-100 nm) is formed by a plasma CVD method as a base film 301 on asubstrate 300 having an insulating surface, and a silicon oxynitridefilm with a thickness of 50-200 nm (preferably, 100-150 nm) is laminatedthereon. In the present embodiment, the silicon nitride oxide film isformed in a thickness of 50 mm and the silicon oxynitride film is formedin a thickness of 100 nm by the plasma CVD method. A glass substrate, aquartz substrate, a silicon substrate, a metal substrate or a stainlesssteel substrate having an insulating film formed on the surface thereofmay be used as the substrate 300. Furthermore, a heat-resistant plasticsubstrate capable of withstanding the treatment temperature of thepresent embodiment may be also used, and a flexible substrate may bealso used. A two-layer structure may be also used as the base film, anda single-layer film or a multilayer structure including two or morelayers of the base (insulating) film may be used.

A semiconductor film 360 is then formed on the base film. Thesemiconductor film may be formed in a thickness of 25-200 nm(preferably, 30-150 nm) by well-known means (sputtering method, LPCVDmethod, plasma CVD method, or the like). The material of thesemiconductor film 360 is not limited, but it is preferably formed fromsilicon, a silicon-germanium (SiGe) alloy, or the like.

In the present embodiment, an amorphous silicon film was formed by aplasma CVD method in a thickness of 54 nm as the semiconductor film 360.In the present embodiment, a thermal crystallization method and a lasercrystallization method using a metal element for enhancing thecrystallization of the amorphous silicon film is conducted, butalternatively laser crystallization may be also conducted by reducingthe concentration of hydrogen contained in the amorphous silicon film to1×10²⁰ atoms/cm³ or less by heating for 1 h at a temperature of 500° C.in a nitrogen atmosphere, without introducing a metal element into theamorphous silicon film. This is because, if an amorphous silicon filmcontaining a large amount of hydrogen is illuminated with a laser beam,the film is destructed.

Nickel is used as the metal element and introduced on the amorphoussilicon film by a solution coating method. The method for introducingthe metal element into the amorphous silicon film is not limitedespecially, provided that the metal element can be caused to be presenton the surface of or inside the amorphous silicon film. For example, asputtering method, a CVD method, a plasma treatment method (including aplasma CVD method) a desorption method, and a method for coating asolution of a metal salt can be used. Among them, the method using asolution has good utility because it is simple and allows theconcentration of the metal element to be easily adjusted. Furthermore,it is preferred that an oxide film be formed by irradiation with UVlight in oxygen atmosphere, thermal oxidation method, treatment withhydrogen peroxide or ozonized water containing hydroxy radicals, or thelike in order to improve the wettability of the surface of the amorphoussemiconductor film and spread the aqueous solution over the entiresurface of the amorphous silicon film.

Heat treatment is then conducted for 4-20 h at a temperature of 500-550°C. and the amorphous silicon film is crystallized. In the presentembodiment, nickel was used as the metal element, a metal-containinglayer was formed and introduced on the amorphous silicon film by asolution coating method, and a first crystalline silicon film wasobtained by conducting heat treatment for 4 h at a temperature of 550°C.

Crystallization is then enhanced by illuminating the first crystallinesilicon film with laser light, and a second crystalline silicon film isobtained. With the laser crystallization method, a semiconductor film isilluminated with laser light. The laser used is preferably a solidlaser, a gas laser, or a metal laser with pulsed or continuousoscillation. Examples of a solid laser include, a YAG laser, a YVO₄laser, a YLF laser, a YAlO₃ laser, a glass laser, a ruby laser, analexandrite laser, and a Ti-sapphire laser. Examples of a gas laserinclude an excimer lasers, an Ar laser, a Kr laser, and a CO₂ laser, andexamples of a metal laser include a helium-cadmium laser, a copper vaporlaser, and a gold vapor laser. The laser beam can be converted intohigher harmonics with a nonlinear optical element. In terms ofconversion efficiency, excellent results are obtained if, for example,crystals called LBO, BBO, KDP, KTP, KB5, or CLBO are used for thenonlinear optical element. The conversion efficiency can be greatlyincreased if those nonlinear optical elements are placed into the laserresonator. In higher harmonics lasers, Nd, Yb, Cr, or the like isgenerally doped, and laser is oscillated when it is excited. The dopanttype may be appropriately selected by a user. A semiconductor film maybe an amorphous semiconductor film, a microcrystalline semiconductorfilm, and a crystalline semiconductor film. A compound semiconductorfilm having an amorphous structure such as an amorphoussilicon—germanium film and an amorphous silicon carbide film may beemployed.

The crystalline semiconductor film 360 thus obtained is doped with aminute amount of dopant element (boron or phosphorus) to control thethreshold voltage of a TFT (FIG. 4A).

The present invention is used in the doping process.

Preprocessing of the semiconductor film 360 is conducted in apreprocessing chamber. The preprocessing is conducted to expose thesurface of the semiconductor layer and measure a correct contact angle.Therefore, the preprocessing may be omitted if the surface of thesemiconductor layer has been already exposed. In the present embodiment,a silicon film, which is easy to oxidize, is used for the semiconductorlayer. Therefore, the silicon film is oxidized and an oxide film isformed on the surface. This oxide film is removed with hydrofluoric acid(HF). This treatment with hydrofluoric acid exposes the surface of thesemiconductor layer and prepares it for measuring the contact angle. Thepretreated semiconductor layer is transported into a contact anglemeasurement chamber where the contact angle is measured with a contactangle measurement device.

In the silicon film used in the present embodiment, the oxide filmetching conducted with hydrofluoric acid as a preprocessing decreasesthe number of hydroxyl groups on the surface. As a result, the surfaceof the silicon film treated with hydrofluoric acid is terminated with amonomolecular film of hydrogen and a contact angle with respect to waterincreases. In other words, the surface becomes hydrophobicity.

If the semiconductor film taking on hydrophobicity is doped with adopant, then a contact angle varies depending on the carrierconcentration in the semiconductor film and the conductivity type of thecarrier. When a silicon film is doped with boron and phosphorus, acontact angle increases as the concentration of phosphorus rises in caseof phosphorus, and a contact angle decreases as the concentration ofboron rises in case of boron. Therefore, the activation ratio andconductivity type of the carrier in a semiconductor layer can beclarified by a contact angle.

This information is used to verify whether the carrier concentration andconductivity type allow the desired characteristics to be obtained, anddoping of a dopant element (boron or phosphorus) is carried out ifnecessary. A contact angle is measured again after doping, and thedoping process is conducted by feeding back the information till thecarrier concentration and conductivity type thereof are optimized. Thesemiconductor film for which the carrier concentration and conductivitytype were optimized is advanced to subsequent processing.

In accordance with the present invention, the characteristics of asemiconductor can be measured non-destructively and in an easy manner,and optimum carrier concentration and conductivity type thereof can beobtained by feeding back the information. Because of the non-destructiveinspection and simple manner, in-situ measurements can be conducted onsubstrates in an actual production line. Because monitoring can beconducted on actual fabricated substrates, inaccuracy of measurements isextremely small.

Further, the characteristics of the semiconductor can be momentarily andaccurately comprehended non-destructively and in an easy manner byin-situ monitoring the characteristics, and doping can be conductedunder optimum conditions allowing the desired characteristics to beobtained by feeding back this information to the process. Therefore,there is no time lag in the feedback and the yield is also increased.

Semiconductor layers 305-308, 361-364 are formed by patterning usingphotolithography (FIG. 4B). Referring to FIG. 4B, the semiconductorlayers 361-364 in the measurement region represent the measurementregion for monitoring carrier concentration in accordance with thepresent invention. Therefore, in the present embodiment, because dopantregions of four types with different carrier concentrations arefabricated, four semiconductor layers are formed, but the presentinvention is not limited to the present embodiment, and the appropriatemeasurement region may be provided according to respective a process ora structure.

A gate insulating film 309 covering the semiconductor layers 305-308 isformed. The gate insulating film 309 is formed from an insulating filmcontaining silicon and having a thickness of 40-150 nm by using a plasmaCVD method or sputtering method. In the present embodiment, a siliconoxynitride film with a thickness of 115 nm was formed by a plasma CVDmethod. It goes without saying, that the gate insulating film is notlimited to the silicon oxynitride film, and other insulating films maybe used as a single layer or as a laminated structure.

A first conductive film with a thickness of 20-100 nm and a secondconductive film with a thickness of 100-400 nm are then formed on thegate insulating film. The first conductive film and second conductivefilm may be formed from an element selected from the group consisting ofTa, W, Ti, Mo, Al, and Cu, or from an alloy material or a compoundmaterial containing those elements as the main components. Furthermore,a semiconductor film represented by a polycrystalline silicon film dopedwith a dopant element such as phosphorus or a AgPdCu alloy may be alsoused for the first conductive film and second conductive film.Furthermore, the film is not limited to the two-layer structure. Forexample a three-layer structure obtained by laminating a tungsten filmwith a thickness of 50 nm, an aluminum-silicon alloy (Al—Si) film with athickness of 500 nm, and a titanium nitride film with a thickness of 30nm in the order of description may be used. When a three-layer structureis used, tungsten nitride may be used instead of tungsten of the firstconductive film, an aluminum-titanium alloy film (Al—Ti) may be usedinstead of the aluminum-silicon alloy (Al—Si) film of the secondconductive film, and a titanium film may be used instead of the titaniumnitride film of the third conductive film. A single-layer structure maybe also employed. Further, in the present embodiment, a tantalum nitridefilm with a thickness of 30 nm and a tungsten film with a thickness of370 nm were formed by lamination in the order of description on the gateinsulating film 309 (FIG. 4C). In this case, in the present embodiment,in the semiconductor layers 361-364 of the measurement region, after thefirst conductive layer 301 has been formed, it was covered with a mask401, and the second conductive layer 311 was not formed.

A mask composed of a resist is then formed by using photolithography,and a first etching treatment for forming electrodes and wiring isconducted. The first conductive film and the second conductive film canbe etched to the desired tapered shape by using an ICP (InductivelyCoupled Plasma) etching method and appropriately adjusting the etchingconditions (electric energy applied to coil electrodes, electric energyapplied to electrodes on the substrate side, temperature of electrodeson the substrate side, or the like). Chlorinated gases represented byCl₂, BCl₃, SiCl₄, CCl₄, fluorinated gases represented by CF₄, SF₆, NF₃,or the like, or O₂ can be appropriately used.

Conductive layers (first conductive layer and second conductive layer)of a first shape composed of the first conductive layer and secondconductive layer are formed by the first etching treatment.

Then, a second etching treatment is conducted without removing masks365, 366, 367 a, 367 b, 368, and 377 composed of a resist. Here, a Wfilm is selectively etched. At this time, the second conductive layers322 b-326 b are formed by the second etching treatment. On the otherhand, the first conductive layers 322 a-326 a are practically notetched, and in the measurement region for forming the conductive layers322-326 of a second shape, a mask 377 composed of a resist is formedonly on the semiconductor layer 364 and the first conductive layerspresent on the semiconductor layers 361-363 are removed by etching (FIG.5A).

Then, the first doping treatment is conducted without removing the maskcomposed of the resist, and a dopant element providing the n-typeconductivity is added at a low concentration level to the semiconductorlayer (FIG. 5B). The doping treatment may be carried out by an iondoping method or an ion injection method. Elements of a Group 15,represented by phosphorus (P) or arsenic (As), are used as the dopantelement providing the n-type conductivity, but here phosphorus (P) isused. In this case, the mask 377 composed of a resist and the conductivelayers 322-326 serves as the mask with respect to the dopant elementproviding the n-type conductivity, and dopant regions 369-375 are formedwith self-aligning. In the dopant region, the dopant element providingthe n-type conductivity is added within a concentration range of1×10¹⁸−1×10²⁰/cm³.

In order to measure the concentration of carriers in thislow-concentration dopant region, the gate insulating film 309 located onthe dopant region 373 is removed by etching, pretreatment is carried outto expose the surface, a contact angle of water with the dopant region373 of the semiconductor layer is measured and analyzed, and theconcentration of carriers in the low-concentration dopant region ismeasured. The conductivity type of the carriers can be also made clearbased on a contact angle, but in the present embodiment, theconductivity type of the carriers is the n type because phosphorusproviding the n-type conductivity has been doped. Because in the case ofphosphorus, a contact angle increases with the increase in carrierconcentration, when the measured value of a contact angle is less thanthat of the contact angle corresponding to the desired carrierconcentration, additional doping has to be carried out. Thus, inaccordance with the present invention, feedback can be conducted in thecourse of the doping process, without a time lag. Therefore, a dopantregion having the optimum carrier concentration can be formed.

After the masks 365-368 and 377 composed of a resist have been removed,masks 378, 379 a, 379 b, and 381 composed of a resist are newly formed,and a second doping treatment is carried out at an accelerating voltagehigher than that of the first doping treatment. In this dopingtreatment, the second conductive layer 323 b is used as a mask for thedopant element, and doping is conducted so that the dopant element isadded to the semiconductor layer below the tapered portion of the firstconductive layer. Then, the accelerating voltage is lowered with respectto that of the second doping treatment and a third doping treatment isconducted. As a result of the second doping treatment and the thirddoping treatment, a dopant element providing the n-type conductivity isadded in a concentration range of 1×10¹⁸−5×10¹⁹/cm³ to alow-concentration dopant region 383 which overlaps the firstelectrically conductive layer, and a dopant element providing the n-typeconductivity is added in a concentration range of 1×10¹⁹−5×10²¹/cm³ tohigh-concentration dopant regions 382, 384, 386 (FIG. 5C).

It goes without saying that with an appropriate acceleration voltage,the second doping treatment and the third doping treatment can also formthe low-concentration dopant region and the high-concentration dopantregion by a single doping treatment.

The high-concentration dopant region 386 is used to monitor theoptimization of the carrier concentration of the high-concentrationdopant regions 382, 384. As with the process relating to thelow-concentration dopant region, the gate insulating film 309 is removedby etching so that the surface of the high-concentration dopant region386 is exposed, and the surface of the dopant region 400 is treated.Then, a contact angle with water is measured and analyzed and thecarrier concentration of the high-concentration dopant region ismeasured. The measurement results are fed back to the doping process toobtain a contact angle corresponding to the desired carrierconcentration. Thus, in accordance with the present invention, becausein-situ evaluation is conducted and feedback can be carried out in thecourse of the doping process, without a time lag, a dopant region havingthe optimum carrier concentration can be formed.

Then, after the mask composed of a resist has been removed, masks 387,389 and 390 are newly formed of a resist and a fourth doping treatmentis conducted. This fourth doping treatment forms dopant regions 391-396having added a dopant element providing a conductivity type which isopposite to the aforementioned conductivity type in the semiconductorlayer serving as an active layer of a p-channel TFT (FIG. 9A).Furthermore, if the semiconductor layers 385 and 400 are not used assensors, as in the present embodiment, then the formation of the mask390 composed of a resist may be omitted. Furthermore, a dopant may beeven introduced into semiconductor layers 385 and 400 to obtain carrierconcentration monitors for other dopant regions and an appropriatedesign may be made. The first and second conductive layers 322 a, 322 b,326 a, and 326 b are used as masks for the dopant elements and thedopant regions are formed with self-aligning by adding the dopantelement providing the p-type conductivity. In the present embodiment,the dopant regions (low-concentration dopant region orhigh-concentration dopant region) 391-396 are formed by an ion dopingmethod using diborane (B₂H₆). During this fourth doping treatment, thesemiconductor layer forming the n-channel TFT is covered with a maskcomposed of a resist. With the first to third doping treatments,phosphorus is added to the dopant region at respective differentconcentrations, but conducting the doping treatment so that theconcentration of the dopant element providing the p-type conductivitybecomes 1×10¹⁹−5×10²¹ atoms/cm³ in all the regions, eliminates anyproblems relating to those dopant regions functioning as the sourceregion and the drain region of the p-channel TFT.

Further, in the present embodiment, the dopant region 396 is used as thecarrier concentration monitor of the low-concentration dopant regions392 and 394 providing the p-type conductivity, and the dopant region 395is used as the carrier concentration monitor of the high-concentrationdopant regions 391 and 393 providing the p-type conductivity. Thecarrier concentration is optimized by using the present invention in thesame manner as in the dopant region providing the n-type conductivity.

In order to measure the concentration of carriers in this p-type dopantregion, the gate insulating film 309 located on the dopant regions 395and 396 and the first conductive layer 310 located over the dopantregion are removed by etching, preprocessing is carried out to exposethe surface, a contact angle of water with the dopant regions 398 and399 is measured and analyzed, and the concentration of carriers in therespective dopant regions is measured. The conductivity type of thecarriers can be also made clear based on a contact angle, but in thepresent embodiment, the conductivity type of the carriers is the p typebecause boron, which is a p-type dopant, is doped. Because a contactangle decreases with the increase in carrier concentration provided byboron, when the measured value of a contact angle is higher than that ofa contact angle corresponding to the desired carrier concentration,additional doping has to be carried out. The concentration of carriersin the high-concentration dopant regions 391 and 393 and thelow-concentration dopant regions 392 and 394 providing the p-typeconductivity is thus optimized. Thus, in accordance with the presentinvention, feedback is conducted in the course of the doping process,without a time lag. Therefore a dopant region having the optimum carrierconcentration can be formed.

Dopant regions are formed in respective semiconductor layers by theabove-described processes.

An insulating film 349 is then formed as a passivation film afterremoving the mask composed of the resist (FIG. 9B). A insulating filmcontaining silicon and having a thickness of 100-200 nm is formed as theinsulating film 349 by using a plasma CVD method or a sputtering method.It goes without saying, that the insulating film 349 is not limited to asilicon oxynitride film, and other insulating films comprising siliconmay be used as a single layer or a multilayer structure. In the presentembodiment, a silicon nitride oxide film with a thickness of 150 nm isformed by a plasma CVD.

Then, heat treatment is conducted for 1-12 h at a temperature of300-550° C. in a nitrogen atmosphere and a process of hydrogenating thesemiconductor layer is carried out. The process is preferably carriedout at a temperature of 400-500° C. This is the process in whichdangling bonds of the semiconductor layer are terminated with hydrogencontained in the first insulating film 349. In the present embodiment,the heat treatment is conducted for 1 h at a temperature of 410° C.

The insulating film 349 is formed of a material selected from substancescomprising silicon nitride, silicon oxide, silicon oxynitride (SiON),silicon nitride oxide (SiNO), aluminum nitride (AlN), aluminumoxynitride (AlON), aluminum nitride oxide with a content of nitrogenhigher than the content of oxygen, aluminum oxide, diamond-like carbon(DLC), nitrogen-containing carbon film (CN), and siloxane-basedpolymers.

Further, in accordance with the present invention, a film containing Si25-35 at.%, oxygen 55-65 at.%, nitrogen 1-20 at. %, and hydrogen 0.1-10at.% is shown as a silicon oxynitride (SiON) film, and a film containingSi 25-35 at.%, oxygen 15-30 at.%, nitrogen 20-35 at.%, and hydrogen15-25 at.% is shown as a silicon nitride oxide (SiNO) film.

Heating treatment, irradiation with high-intensity light, andirradiation with laser light may be carried out for activating thedopant element. Restoration of plasma damage of the gate insulating filmor plasma damage of the interface of the gate insulating film and thesemiconductor layer can be conducted simultaneously with the activation.

Further, an interlayer film 350 comprising an organic resin material isformed on the insulating film 349. The interlayer film 350 is a filmcomposed of an inorganic material (silicon oxide, silicon nitride,silicon oxynitride, silicon nitride oxide, and the like), aphotosensitive or non-photosensitive organic resin material (organicresin material) (polyimide, acryl, polyamide, polyimidoamide, resist,benzocyclobutene, siloxane polymer, and the like), or several suchmaterials. A laminate composed of such films can be also used.Furthermore, a photosensitive negative-type material which becomesinsoluble in an etchant under light irradiation, or a photosensitivepositive-type material which becomes soluble in an etchant under lightirradiation can be used for the interlayer film. In the presentembodiment, a positive-type photosensitive acryl which is aphotosensitive organic resin material is used. In this case, it ispreferred that a curved surface having a curvature radius of 0.2 μm to 3μm be provided only at the upper end portion of the interlayer film. Apassivation film composed of silicon nitride, silicon oxide, siliconoxynitride (SiON), silicon nitride oxide (SiNO), aluminum nitride (AlN),aluminum oxynitride (AlON), aluminum nitride oxide (AlNO) with anitrogen content higher than the oxygen content, aluminum oxidediamond-like carbon (DLC), nitrogen-containing carbon film (CN), and asiloxane-based polymer may be thereafter formed on the interlayer film350.

The interlayer film 350, the insulating film 349, and the gateinsulating film 309 are etched and holes reaching the source region anddrain region are formed. The holes may be formed by etching theinterlayer film and then again forming a mask, or by using the etchedinterlayer film 350 as a mask and etching the insulating film 349 andthe gate insulating film. A metal film is formed, and a source electrodeor a drain electrode 352, and wiring (not shown in the figure)electrically connected to respective dopant regions are formed byetching the metal film. The metal film may be a film composed ofaluminum (Al), titanium (Ti), molybdenum (Mo), tungsten (W), or silicon(Si), or an alloy film using those elements. Further, in the presentembodiment, a titanium film, a silicon-aluminum alloy film, and atitanium film (Ti/Si—Al/Ti) are laminated at 100/350/100 nm,respectively, and then the source electrode or the drain electrode 352and wiring (not shown in the figure) are formed by patterning andetching to a desired shape.

A pixel electrode 353 is then formed. In the present embodiment, atransparent conductive film is formed and the pixel electrode 353 isformed by etching the film to a desired shape (FIG. 9C). In the presentembodiment, a measurement region having a semiconductor layer that willserve as a monitor is formed, and once the carrier concentration of thedopant region has been optimized and the monitoring function becomesunnecessary, this region may be removed or may be left as is on thesubstrate. The operator can make an appropriate decision according tothe structure and design of the display device which is to befabricated.

A compound of indium oxide and tin oxide, a compound of indium oxide andzinc oxide, zinc oxide, tin oxide, or indium oxide can be used for thetransparent conductive film. Furthermore, a transparent conductive filmadditionally containing gallium may be used. The pixel electrode 353 maybe formed on a flat interlayer insulating film prior to forming theaforementioned wiring. An effective method is to flatten the stepcreated due to a TFT by using a planarizing film composed of a resin.Because a light-emitting layer which is to be formed thereafter is verythin, the presence of the step sometimes causes emission defect.Therefore, flattening is preferably conducted prior to forming the pixelelectrodes so that the light-emitting layer is formed to have a surfaceas flat as possible.

The above-described process produces an active matrix substrate equippedwith a TFT. In the present embodiment, the n-channel TFT of a pixelregion is used a double-gate structure in which two channel formationregions are formed, but a single-gate structure in which one channelformation region is formed or a triple-gate structure in which threechannel formation regions are formed may be also used. Furthermore, theTFT of a drive circuit portion has a single-gate structure in thepresent embodiment, but it may also have a double-gate structure ortriple-gate structure.

The present invention is not limited to the TFT fabrication methoddescribed in the present embodiment and can be applied to a top-gatestructure (planar structure), bottom-gate structure (inverted staggerstructure), dual-gate structure which has two gate electrodes disposedvia a gate insulating film above and below the channel region, and otherstructures.

Embodiment 2

In the present embodiment an example of the fabrication of alight-emitting display device using an active matrix substratefabricated in Embodiment 1 will be explained. In accordance with thepresent invention, a light-emitting display device is a generic termapplied to a display panel in which light-emitting elements formed on asubstrate are inserted between the substrate and a cover material and toa display module in which TFT are provided on the aforementioned displaypanel. The light-emitting element has a layer (light-emitting layer)comprising an organic compound capable of producing EL, an anode layer,and a cathode layer. The luminescence in an organic compound includeslight emission (fluorescence) induced by the return from a singletexcitation state to a ground state and light emission (phosphorescence)induced by the return from a triplet excitation state to a ground state.Any of light-emitting materials which emits light through singletexcitation, triplet excitation or both of them may be used for ELmaterial in accordance with the invention.

Further, in accordance with the present invention, all the layers formedbetween the anode and the cathode in a light-emitting element aredefined as organic light-emitting layers. More specifically, the organiclight-emitting layers include a light-emitting layer, a hole injectionlayer, an electron injection layer, a hole transport layer, an electrontransport layer, and the like. Basically, the light-emitting element hasa structure in which an anode layer, a light-emitting layer, and acathode layer are stacked in the order of description. There are alsolight-emitting elements having a structure in which an anode layer, ahole injection layer, a light-emitting layer, and a cathode layer arestacked or a structure in which an anode layer, a hole injection layer,a light-emitting layer, an electron transport layer, and a cathode layerare stacked in the order of description.

After the pixel electrode 353 has been formed, an insulator 1012 isformed as shown in FIG. 6. The insulator 1012 may be formed bypatterning silicon-containing insulating film or organic resin film witha thickness of 100-400 nm.

Further, because the insulator 1012 is an insulating film, attentionshould be paid to electrostatic destruction of elements during filmformation. In the present embodiment, the resistivity is decreased andthe generation of electrostatic charges is inhibited by adding carbonparticles or metal particles to the insulating film serving as amaterial for the insulator 1012. In this case, the amount of carbonparticles or metal particles that are added may be adjusted so that theresistivity becomes 1×10⁶−1×10¹² Ohm (preferably, 1×10⁸−10¹⁰ Ohm).

A light-emitting layer 1013 is formed on the pixel electrode 353. Onlyone pixel is shown in FIG. 10, but in the present embodiment thelight-emitting layers corresponding to each color of R (red), G (green),and B (blue) are formed separately. Furthermore, in the presentembodiment, a low-molecular weight organic light-emitting material isformed by a deposition method. More specifically, a laminated structureis obtained in which a copper phthalocyanine (CuPc) film with athickness of 20 nm is provided as a hole injection layer and atris-8-quinolinolate aluminum complex (Alq₃) film with a thickness of 70nm is provided as a light-emitting layer thereupon. The color of emittedlight can be controlled by adding fluorescent dye such as quinacridone,perylene, or DCM 1 to Alq₃.

The above-described examples are only the examples of the organiclight-emitting materials that can be used for the light-emitting layer,and it is absolutely not necessary to be limited thereto. Thelight-emitting layer (a layer for emitting light and inducing themovement of carriers) may be formed by freely combining a light-emittinglayer, a charge transport layer or a charge injection layer. Forexample, in the present embodiment an example is described in which alow-molecular weight organic light-emitting material is used for thelight-emitting layer. However, organic medium-molecular weight orhigh-molecular weight light-emitting materials may be also used.Further, in the present specification, an organic light-emittingmaterial having no sublimation ability and a number of molecules of 20or less or a molecular chain length of 10 μm or less is considered as amedium-molecular weight organic light-emitting material. As an exampleof using a high-molecular weight organic light-emitting material, alaminated structure may be considered in which a 20 nm polythiophene(PEDOT) film is provided as a hole injection layer by a spin coatingmethod and a paraphenylene vinylene (PPV) film with a thickness of about100 nm is provided thereupon as a light-emitting layer. Further,emission wavelength can be selected from red color to blue color byusing a PPV π-conjugated polymer. Further, an inorganic material such assilicon carbide can be also used as a charge transport layer or a chargeinjection layer. Well-known materials can be used as the aforementionedorganic light-emitting materials or inorganic materials.

A cathode 1014 composed of a conductive film is then formed on thelight-emitting layer 1013. A material with a low work function (Al, Ag,Li, Ca, or alloys thereof such as MgAg, MgIn, AlLi, CaF₂, or CaN) may beused for the cathode. In the present embodiment, a laminate of a thinmetal film of reduced thickness (MgAg: film thickness 10 nm) and atransparent conductive film with a thickness of 110 nm (ITO (indiumoxide-tin oxide alloy), indium oxide-zinc oxide alloy, zinc oxide, tinoxide, or indium oxide) is used as the cathode 1014 to transmit theemitted light.

The formation of a light-emitting element 1015 is completed when thecathode 1014 is formed. The light-emitting element 1015 is formed fromthe pixel electrode (anode) 353, the light-emitting layer 1013, and thecathode 1014.

Providing a passivation film 1022 is effective for completely coveringthe light-emitting element 1015. Insulating films of silicon nitride,silicon oxide, silicon oxynitride (SiON), silicon nitride oxide (SiNO),aluminum nitride (AlN), aluminum oxynitride (AlON), aluminum nitrideoxide with a nitrogen content higher than a oxygen content, aluminumoxide, diamond-like carbon (DLC), nitrogen-containing carbon film (CN),and a siloxane-based polymer can be used in the structure of a singlelayer or combined laminates as the passivation film.

It is preferred that a film with good coverage be used as thepassivation film, and using a carbon film, especially, a DLC film iseffective. A DLC film can be formed at a temperature within a range offrom room temperature to less than 100° C. Therefore, it can be easilyformed on the light-emitting layer 1013 which has low heat resistance.Furthermore, DLC films demonstrate good blocking effect with respect tooxygen and can inhibit oxidation of the light-emitting layer 1013.Therefore, a problem of the light-emitting layer 1013 being oxidizedwhile the subsequent sealing process is conducted can be prevented.

No specific limitation is placed on a sealing material 1017. Typicallyit is preferred that an indurative resin with visible light, anindurative resin with UV ray, or a thermosetting resin is used. In thepresent embodiment, a thermosetting epoxy resin is used. Furthermore, inthe present embodiment a glass substrate, a quartz substrate, a plasticsubstrate (including plastic films), or a flexible substrate havingcarbon films (preferably, DLC films or CN films) formed on both surfacesthereof is used as a cover material 1021. Besides the carbon films,aluminum-containing films (AlON, AlN, AlO, and the like) or SiN can beused. As a result, a light-emitting display device of a dual-sidedemission type which has a structure shown in FIG. 6 is obtained.

In the present embodiment, a dual-sided emission type is described inwhich light is emitted from both sides of a light-emitting displaydevice, but a single-sided emission system is also possible. When lightis emitted from the side of the cathode 1014, the pixel electrode 353 isa metal film having reflectivity and equivalent to an anode. A metalfilm with a high work function, such as platinum (Pt) or gold (Au), isused to function as an anode for the metal film having reflectivity.Furthermore, because those metals are expensive, a pixel electrode maybe used in which the metals are laminated on the appropriate metal filmsuch as an aluminum film or a tungsten film, so that platinum or gold isexposed on the outermost surface. Furthermore, the cathode 1014 is athin (preferably 10-50 nm) metal film and a material comprising anelement belonging to Group 1 or Group 2 of the periodic table of theelements that has a low metal work function, which is necessary for thematerial to serve as a cathode (for example, Al, Ag, Li, Ca, or alloysthereof such as MgAg, MgIn, AlLi, CaF₂, or CaN), is used therefor.Further, an oxide conductive film (typically, an ITO film) which is thecathode 1014 is provided by lamination on the cathode 1014. In thiscase, the light emitted from the light-emitting element is reflected bythe pixel electrode 353 and emitted via the cathode 1014.

When light is emitted only from the side of the pixel electrode 353, atransparent conductive film is used for the pixel electrode 353 which isequivalent to an anode. A compound of indium oxide and tin oxide, acompound of indium oxide and zinc oxide, zinc oxide, tin oxide, orindium oxide can be used as the transparent conductive film.Furthermore, a metal film (thickness 50 nm to 200 nm) composed of Al,Ag, Li, Ca, or alloys thereof such as MgAg, MgIn, or AlLi is preferablyused for the cathode 1014. In this case, the light emitted from thelight-emitting element is emitted via the pixel electrode 353 from theside of the substrate 300.

Further, in the present embodiment, the semiconductor element fabricatedby using the doping method and doping apparatus in accordance with thepresent invention is applied to a light-emitting display device using alight-emitting element. However, the semiconductor element in accordancewith the present invention can be also applied to liquid-crystal displaydevices using liquid crystal. In both cases, the present invention makesit possible to fabricate a highly reliable display device demonstratingthe desired characteristics with good yield.

The process prior to the formation of the passivation film after theinsulator 1012 has been formed can be effectively implemented in acontinuous mode without releasing the atmosphere, by using a filmforming apparatus of a multi-chamber system (or inline system). Furtherexpanding the procedure, the process prior to pasting the cover material1021 can be implemented continuously without releasing the atmosphere.

Furthermore, providing a dopant region to a gate electrode via aninsulating film makes it possible to form an n-channel TFT with a highresistance to degradation induced by a hot carrier effect. Therefore, ahighly reliable display device can be realized.

Further, in the present embodiment only the configuration of the pixelportion and the drive circuit is described, but according to themanufacturing process of the present embodiment, other logic circuitssuch as a signal splitting circuit, a D/A converter, an operationamplifier, and a γ correction circuit can be formed on the sameinsulator. Moreover, a memory or a microprocessor can be also formed.

With the present invention, a highly reliable display device having thedesired characteristics can be fabricated with an appropriate dopingapparatus and a doping method. Furthermore, in a doping apparatus and adoping method in accordance with the present invention, the informationon carrier concentration and conductivity type thereof can be fed backwith a nondestructive and simple measurement method. Therefore, displaydevices such as a light-emitting display device or a liquid-crystaldisplay device can be fabricated with good yield.

Embodiment 3

A variety of display devices (an active matrix type display device andan active matrix type EC display device) can be fabricated in accordancewith the present invention. In other words, the present invention isapplied to various electronic devices in which the display device isincorporated on the display portion.

Such an electronics device using the present invention includes a videocamera, a digital camera, a projector, a head mounted display (a goggletype display), a car navigation system, a car audio system, a personalcomputer, a Personal Digital Assistant (a mobile computer, a cellularphone or an electronic book), or the like. These examples are shown inFIGS. 7A to 7F and FIGS. 8A to 8C.

FIG. 7A is a personal computer including a body 3001, an image inputportion 3002, a display portion 3003, a keyboard 3004, and the like. Adisplay device fabricated in the present invention is applied to thedisplay portion 3003 and thereby a personal computer of the presentinvention is achieved.

FIG. 7B is a video camera including a body 3101, a display portion 3102,an audio input portion 3103, operating switches 3104, a battery 3105, animage receiving portion 3106, and the like. A display device fabricatedin the present invention is applied to the display portion 3102 andthereby a video camera of the present invention is achieved.

FIG. 7C is a mobile computer including a body 3201, a camera portion3202, an image receiving portion 3203, an operating switch 3204, adisplay portion 3205, and the like. A display device fabricated in thepresent invention is applied to the display portion 3205 and thereby amobile computer of the present invention is achieved.

FIG. 7D is a goggle type display including a body 3301, display portions3302, an arm portion 3303, and the like. A flexible substrate is used asa substrate in the display portion 3302, and a goggle type display isfabricated with the bent display portion 3302. In addition, a goggletype display, which is lightweight and thin, is achieved. A displaydevice fabricated in the present invention is applied to the displayportions 3302 and thereby a goggle type display of the present inventionis achieved.

FIG. 7E is a player utilizing a recording medium that has a programrecorded (hereinafter referred to as a recording medium) including abody 3401, a display portion 3402, a speaker portion 3403, a recordingmedium 3404, an operating switch 9705, and the like. It is noted thatthis player makes it possible to enjoy listening to the music, watchingthe movie, playing the game, and playing on the Internet using a DVD(Digital Versatile Disc), CD, or the like as the recording medium. Adisplay device fabricated in the present invention is applied to thedisplay portion 3402 and thereby a recording medium of the presentinvention is achieved.

FIG. 7F is a digital camera including a body 3501, a display portion3502, an eye piece 3503, operating switches 3504, an image receivingportion (not shown in the figure), and the like. A display devicefabricated in the present invention is applied to the display portion3502 and thereby a digital camera of the present invention is achieved.

FIG. 8A is a cellular phone including a body 3901, a voice outputportion 3902, a voice input portion 3903, a display portion 3904,operating switches 3905, an antenna 3906, and the like. A display devicefabricated in the present invention is applied to the display portion3904 and thereby a cellular phone of the present invention is achieved.

FIG. 8B is a mobile book (an electronic book) including a body 4001,display portions 4002 and 4003, a recording medium 4004, an operatingswitch 4005, and an antenna 4006, and the like. A display devicefabricated in the present invention is applied to the display portions4002 and 4003, and thereby a mobile book of the present invention isachieved.

FIG. 8C is a display including a body 4101, a supporting stand 4102, adisplay portion 4103, and the like. A flexible substrate is used as asubstrate in the display portion 4103 and the display, which islightweight and thin, is achieved. In addition, the display can befabricated with the bent display portion 4103. A display devicefabricated in the present invention is applied to the display portion4103 and thereby a display of the present invention is achieved.

As described above, the present invention can be applied to variouskinds of devices, and can be applied to the electronics device in everyfield. Further, an electronic device described in this embodiment mayuse a light-emitting device having a structure shown in any one ofEmbodiments 1 to 3.

1. A doping method comprising: doping a dopant element providing oneconductivity type to a semiconductor layer; dropping a liquid drop onthe semiconductor layer; measuring a contact angle of the liquid drop onthe semiconductor layer; obtaining information of a conductivity typeand a carrier concentration of the semiconductor layer from the measuredcontact angle; and further doping a required amount of the dopantelement to the semiconductor layer in accordance with the information ofthe conductivity type and the carrier concentration.
 2. A method forfabricating a thin film transistor comprising: forming a conductivelayer adjacent to a first semiconductor layer and a second semiconductorlayer with a gate insulating film interposed therebetween; doping adopant element providing one conductivity type to the firstsemiconductor layer and the second semiconductor layer; dropping aliquid drop on the second semiconductor layer; measuring a contact angleof the liquid drop on the second semiconductor layer; obtaininginformation of a conductivity type and a carrier concentration of thefirst semiconductor layer from the measured contact angle; and furtherdoping a required amount of the dopant element to the firstsemiconductor layer in accordance with the information of theconductivity type and the carrier concentration.
 3. A method forfabricating a thin film transistor comprising: forming a conductivelayer adjacent to a first semiconductor layer and a second semiconductorlayer with a gate insulating film interposed therebetween; doping adopant element providing one conductivity type to the firstsemiconductor layer and the second semiconductor layer; exposing asurface of the second semiconductor layer by etching the gate insulatingfilm; dropping a liquid drop on the surface of the second semiconductorlayer; measuring a contact angle of the liquid drop on the surface ofthe second semiconductor layer; obtaining information of a conductivitytype and a carrier concentration of the first semiconductor layer fromthe measured contact angle; and further doping a required amount of thedopant element to the first semiconductor layer in accordance with theinformation of the conductivity type and the carrier concentration. 4.The doping method according to claim 1, wherein the liquid dropcomprises water.
 5. The method for fabricating a thin film transistoraccording to claim 2, wherein the liquid drop comprises water.
 6. Themethod for fabricating a thin film transistor according to claim 3,wherein the liquid drop comprises water.
 7. The doping method accordingto claim 1, wherein the dopant element is phosphorous.
 8. The method forfabricating a thin film transistor according to claim 2, wherein thedopant element is phosphorous.
 9. The method for fabricating a thin filmtransistor according to claim 3, wherein the dopant element isphosphorous.
 10. The doping method according to claim 1, wherein thedopant element is boron.
 11. The method for fabricating a thin filmtransistor according to claim 2, wherein the dopant element is boron.12. The method for fabricating a thin film transistor according to claim3, wherein the dopant element is boron.
 13. The method for fabricating athin film transistor according to claim 3, wherein an oxide film formedon the surface of the second semiconductor layer is chemically removed.14. The doping method according to claim 1, wherein the contact angle ismeasured via a camera.
 15. The method for fabricating a thin filmtransistor according to claim 2, wherein the contact angle is measuredvia a camera.
 16. The method for fabricating a thin film transistoraccording to claim 3, wherein the contact angle is measured via acamera.
 17. The doping method according to claim 1, wherein thesemiconductor layer is a semiconductor layer selected from the groupconsisting of an amorphous semiconductor layer, a microcrystallinesemiconductor layer, and a crystalline semiconductor layer.
 18. Themethod for fabricating a thin film transistor according to claim 2,wherein each of the first and second semiconductor layers is asemiconductor layer selected from the group consisting of an amorphoussemiconductor layer, a microcrystalline semiconductor layer, and acrystalline semiconductor layer.
 19. The method for fabricating a thinfilm transistor according to claim 3, wherein each of the first andsecond semiconductor layers is a semiconductor layer selected from thegroup consisting of an amorphous semiconductor layer, a microcrystallinesemiconductor layer, and a crystalline semiconductor layer.